I've never badmouthed anyone that changed sides, nor have I actually seen anyone do it. I can see why squaddies might frown upon it, though. A squad sort of implies unity, so if your squad doesn't move than neither should you IMO.
As for spies, meh, whatever, I was just throwing it up there. And as for that CV trick, something should be done about that. Yeah yeah, it's just a game, but if there are those that refuse to play by the rules of the game then the game itself begins to break down, doesn't it?